Touch sensing circuit and touch sensing method

Abstract

The present invention discloses a touch-sensing method, applied to a touch-sensing circuit, wherein the touch-sensing circuit includes a detection circuit and a comparison circuit. The touch-sensing method includes: enabling a receiving node to be coupled to a ground during a first discharge period, wherein the receiving node is coupled between the detection circuit and the comparison circuit; enabling the receiving node to obtain a first reference voltage during a first charge period; enabling the receiving node to be coupled to the ground during a second discharge period; and enabling the receiving node to obtain a second reference voltage and producing a sensing result according to the first reference voltage and the second reference voltage by the comparison circuit during a second charge period, wherein the sensing result represents whether a touch event occurs at a first node of the touch-sensing circuit.

What is claimed is: 
     
       1. A touch-sensing circuit, comprising:
 a detection circuit, comprising:
 a first node, arranged to generate a sensing capacitor according to a touch event; 
 a first capacitor, having a first terminal coupled to the first node, and a second terminal coupled to a ground; 
 a second capacitor, having a first terminal coupled to the first node, and a second terminal coupled to a second node; 
 a third capacitor, having a first terminal coupled to the second node, and a second terminal coupled to the ground; 
 a first switch, arranged to be coupled between the first node and the ground; 
 a second switch, arranged to be coupled between the second node and the ground; and 
 a third switch, arranged to couple the first node or the second node to a receiving node; 
 
 a fourth capacitor, having a first terminal coupled to a voltage source, and a second terminal coupled to the receiving node; and 
 a comparison circuit, arranged to produce a sensing result according to a voltage at the receiving node. 
 
     
     
       2. The touch-sensing circuit as claimed in  claim 1 , wherein the capacitance of the first capacitor is smaller than the capacitance of the third capacitor, and the difference between the capacitance of the third capacitor and the capacitance of the first capacitor is less than the capacitance of the sensing capacitor. 
     
     
       3. The touch-sensing circuit as claimed in  claim 1 , wherein the receiving node is arranged to obtain a first reference voltage during a first charge period and obtain a second reference voltage during a second charge period, respectively, and the comparison circuit is further arranged to produce the sensing result according to the first reference voltage and the second reference voltage. 
     
     
       4. The touch-sensing circuit as claimed in  claim 3 , wherein the receiving node is further arranged to be coupled to the ground during a first discharge period and a second discharge period, wherein the first charge period is scheduled after the first discharge period, the second discharge period is scheduled after the first charge period, and the second charge period is scheduled after the second discharge period. 
     
     
       5. The touch-sensing circuit as claimed in  claim 4 , wherein the detection circuit is a first discharge equivalent circuit and the voltage source is 0 volts during the first discharge period, and wherein the first switch is tuned on, the second switch is turned on, and the third switch is arranged to couple the receiving node with the first node to constitute the first discharge equivalent circuit. 
     
     
       6. The touch-sensing circuit as claimed in  claim 4 , wherein the detection circuit is a first charge equivalent circuit and the voltage source is a predetermined voltage during the first charge period, and wherein the first switch is turned off, the second switch is turned on, and the third switch is arranged to couple the receiving node with the first node to constitute the first charge equivalent circuit. 
     
     
       7. The touch-sensing circuit as claimed in  claim 4 , wherein the detection circuit is a second discharge equivalent circuit and the voltage source is 0 volts during the second discharge period, and wherein the first switch is turned on, the second switch is turned on, and the third switch is arranged to couple the receiving node with the second node to constitute the second discharge equivalent circuit. 
     
     
       8. The touch-sensing circuit as claimed in  claim 4 , wherein the detection circuit is a second charge equivalent circuit and the voltage source is a predetermined voltage during the second charge period, and wherein the first switch is turned on, the second switch is turned off, and the third switch is arranged to couple the receiving node with the first node to constitute the second charge equivalent circuit. 
     
     
       9. The touch-sensing circuit as claimed in  claim 4 , wherein the comparison circuit further comprises:
 a comparing capacitor, having a first terminal coupled to the receiving node, and a second terminal; 
 an inverter, having an input terminal coupled to the second terminal of the comparing capacitor, and an output terminal arranged to output the sensing result; and 
 a fourth switch, arranged to be coupled between the first terminal and the second terminal of the inverter. 
 
     
     
       10. The touch-sensing circuit as claimed in  claim 9 , wherein the capacitance of the comparing capacitor is smaller than the difference between the capacitance of first capacitor and the capacitance of the third capacitor. 
     
     
       11. The touch-sensing circuit as claimed in  claim 9 , wherein:
 the fourth switch is arranged to connect the input terminal of the inverter with the output terminal of the inverter for enabling the comparing capacitor to be charged to a comparison voltage according to the first reference voltage during the first charge period; 
 the fourth switch is arranged to decouple the first terminal of the inverter from the output terminal of the inverter for enabling a voltage across the comparing capacitor to be kept at the comparison voltage during second discharge period; and 
 the fourth switch is arranged to decouple the first terminal of the inverter from the output terminal of the inverter for enabling the inverter to produce the sensing result according to the second reference voltage and the comparison voltage during the second charge period. 
 
     
     
       12. A touch-sensing method, applied to a touch-sensing circuit, wherein the touch-sensing circuit comprises a detection circuit and a comparison circuit, the touch-sensing method comprising:
 enabling a receiving node to be coupled to a ground during a first discharge period, wherein the receiving node is coupled between the detection circuit and the comparison circuit; 
 enabling the receiving node to obtain a first reference voltage during a first charge period; 
 enabling the receiving node to be coupled to the ground during a second discharge period; and 
 enabling the receiving node to obtain a second reference voltage and producing a sensing result according to the first reference voltage and the second reference voltage by the comparison circuit during a second charge period, wherein the sensing result represents whether a touch event occurs at the first node of the touch-sensing circuit. 
 
     
     
       13. The touch-sensing method as claimed in  claim 12 , wherein the first charge period is scheduled after the first discharge period, the second discharge period is scheduled after the first charge period, and the second charge period is scheduled after the second discharge period. 
     
     
       14. The touch-sensing method as claimed in  claim 13 , wherein the step of enabling the receiving node to be coupled to the ground during the first discharge period further comprises the step of enabling the detection circuit to constitute a first discharge equivalent circuit to couple the receiving node to the ground by a plurality of switches. 
     
     
       15. The touch-sensing method as claimed in  claim 13 , wherein the step of enabling the receiving node to obtain the first reference voltage during the first charge period further comprises the steps of enabling the detection circuit to constitute a first charge equivalent circuit by a plurality of switches, and providing a predetermined voltage to the touch-sensing circuit to produce the first reference voltage. 
     
     
       16. The touch-sensing method as claimed in  claim 13 , wherein the step of enabling the receiving node to be coupled to the ground during the second discharge period further comprises the step of enabling the detection circuit to constitute a second discharge equivalent circuit to couple the receiving node to the ground by a plurality of switches. 
     
     
       17. The touch-sensing method as claimed in  claim 13 , wherein the step of enabling the receiving node to obtain a first reference voltage during a second charge period further comprises the steps of enabling the detection circuit to constitute a second charge equivalent circuit by a plurality of switches, and providing a predetermined voltage to the touch-sensing circuit to produce the second reference voltage. 
     
     
       18. The touch-sensing method as claimed in  claim 13 , further comprising the step of:
 enabling a comparing capacitor of the comparison circuit to be charged to a comparison voltage according to the first reference voltage during the first charge period; and 
 enabling a voltage across the comparing capacitor to be kept at the comparison voltage during the second discharge period, wherein the step of producing the sensing result according to the first reference voltage and the second reference voltage is achieved by producing the sensing result according to the second reference voltage and the comparison voltage.